The present invention is concerned with an electromagnetic valve, especially for hydraulic brake systems having a slip control.
In conventionally used electromagnetic valves of the type as set out, for example, in DE-OS 37 29 216, valve sleeves are inserted into a valve housing of a steel valve block configuration and formed to be friction locked and sealed therein. When using electromagnetic valves closed in the de-energized normal condition, the valve sleeve forms the actual magnetic core of the magnetic coil. Located in the inner chamber of the valve sleeve is the magnetic armature actuating the needle valve. When used as an electromagnetic valve open in the de-energized basic position, a bushing provided at the fixing seam of the valve sleeve assumes the function of the magnetic core.
The forming of the sleeve is accomplished by means of a tool driven into the valve block housing to establish the friction-locking connection of the valve sleeve, which is thereby clamped between the valve housing and the bushing.
Especially when considering the relatively high hydraulic test pressures within the valve sleeve, the conventional friction-locking fixation of the valve sleeve requires some improvement in order to prevent the valve sleeve from loosening as a result of pressure induced thrust strain occurring between the contact surfaces.
It is, therefore, the object of the invention to enhance the holding force on the contact faces, while at the same time maintaining the friction-locking connection between valve housing, valve sleeve and bushing.